1. Field of the Invention
The present invention relates to load control systems for controlling electrical loads and more particularly to a method of establishing communication in a radio frequency (RF) lighting control system between two or more RF control devices that may be communicating on different frequencies.
2. Description of the Related Art
Control systems for controlling electrical loads, such as lights, motorized window treatments, and fans, are known. Such control systems often use radio frequency (RF) transmission to provide wireless communication between the control devices of the system. Examples of RF lighting control systems are disclosed in commonly-assigned U.S. Pat. No. 5,905,442, issued on May 18, 1999, entitled METHOD AND APPARATUS FOR CONTROLLING AND DETERMINING THE STATUS OF ELECTRICAL DEVICES FROM REMOTE LOCATIONS, and commonly-assigned U.S. Pat. No. 6,803,728, issued Oct. 12, 2004, entitled SYSTEM FOR CONTROL OF DEVICES. The entire disclosures of both patents are hereby incorporated by reference.
The RF lighting control system of the '442 patent includes wall-mounted load control devices, table-top and wall-mounted master controls, and signal repeaters. The control devices of the RF lighting control system include RF antennas adapted to transmit and receive the RF signals that provide for communication between the control devices of the lighting control system. The control devices all transmit and receive the RF signals on the same frequency. Each of the load control devices includes a user interface and an integral dimmer circuit for controlling the intensity of an attached lighting load. The user interface has a pushbutton actuator for providing on/off control of the attached lighting load and a raise/lower actuator for adjusting the intensity of the attached lighting load. The table-top and wall-mounted master controls have a plurality of buttons and are operable to transmit RF signals to the load control devices to control the intensities of the lighting loads.
To prevent interference with other nearby RF lighting control systems located in close proximity, the RF lighting control system of the '442 patent preferably utilizes a house code (i.e., a house address), which each of the control devices stores in memory. It is particularly important in applications such as high-rise condominiums and apartment buildings that neighboring systems each have their own separate house code to avoid a situation where neighboring systems attempt to operate as a single system rather than as separate systems. Accordingly, during installation of the RF lighting control system, a house code selection procedure is employed to ensure that a proper house code is selected. In order to accomplish this procedure, one repeater of each system is selected as a “main” repeater. The house code selection procedure is initialized by pressing and holding a “main” button on the selected one repeater in one of the RF lighting control systems. The repeater randomly selects one of 256 available house codes and then verifies that no other nearby RF lighting control systems are utilizing that house code. The repeater illuminates a light-emitting diode (LED) to display that a house code has been selected. This procedure is repeated for each neighboring RF lighting control system. The house code is transmitted to each of the control devices in the lighting control system during an addressing procedure described below.
Collisions between transmitted RF communication signals may occur in the RF lighting control system when two or more control devices attempt to transmit at the same time. Accordingly, each of the control devices of the lighting control system is assigned a unique device address (typically one byte in length) for use during normal operation. The device addresses are unique identifiers that are used by the devices of the control system to distinguish the control devices from each other during normal operation. The device addresses allow the control devices to transmit the RF signals according to a communication protocol at predetermined times to avoid collisions. The house code and the device address are typically included in each RF signal transmitted in the lighting control system. Further, the signal repeaters help to ensure error-free communication by repeating the RF communication signals such that every component of the system receives the RF signals intended for that component.
After the house code selection procedure is completed during installation of the lighting control system, an addressing procedure, which provides for assignment of the device addresses to each of the control devices, is executed. In the RF lighting control system described in the '442 patent, the addressing procedure is initiated at a repeater of the lighting control system (e.g., by pressing and holding an “addressing mode” button on the repeater), which places all repeaters of the system into an “addressing mode.” The main repeater is responsible for assigning device addresses to the RF control devices (e.g., master controls, wall-mounted load control devices, etc.) of the control system. The main repeater assigns a device address to an RF control device in response to a request for an address sent by the control device.
To initiate a request for the address, a user moves to one of the wall-mounted or table-top control devices and presses a button on the control device (e.g., an on/off actuator of the wall-mounted load control devices). The control device transmits a signal associated with the actuation of the button. This signal is received and interpreted by the main repeater as a request for an address. In response to the request for address signal, the main repeater assigns and transmits a next available device address to the requesting control device. A visual indicator is then activated to signal to the user that the control device has received a system address from the main repeater. For example, lights connected to a wall-mounted load control device, or an LED located on a master control, may flash. The addressing mode is terminated when a user presses and holds the addressing mode button of the repeater, which causes the repeater to issue an exit address mode command to the control system.
Some prior art RF lighting control systems are operable to communicate on one of a plurality of channels (i.e., frequencies). An example of such a lighting control system is described in the aforementioned U.S. Pat. No. 6,803,728. The signal repeater of such a lighting control system is operable to determine the quality of each of the channels (i.e., determine the ambient noise on each of the channels), and to choose a select one of the channels for the system to communicate on. An unaddressed control device communicates with the signal repeater on a predetermined addressing frequency in order to receive the device address and the selected channel. However, if there is a substantial amount of noise on the predetermined addressing frequency, the control devices may not communicate properly with the repeater and configuration of the control devices may be hindered. Therefore, it is desirable to allow the RF lighting control system to communicate on the selected channel during the configuration procedure.